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Articles containing the keyword 'simulation models'.

Category: Research article

article id 671, category Research article
Jouni Vettenranta, Jari Miina. (1999). Optimizing thinnings and rotation of Scots pine and Norway spruce mixtures. Silva Fennica vol. 33 no. 1 article id 671. https://doi.org/10.14214/sf.671
The study describes a simulation-optimization system which uses spatial models for diameter and height growth, crown ratio and tree mortality for Scots pine and Norway spruce mixtures. The optimal one- and two-thinning regimes of six initial stands with varing species composition were solved by using nonlinear optimization. The soil expectation value (SEV) at 3% interest rate was used as a management objective. The regimes are determined by taking into account the stand basal areas before the thinnings, the removal percentages for small, medium-sized and large pines and spruces, and the stand basal area before the final felling. The greatest SEV (8900 FIM ha–1) was attained with the initial stand where the proportion of pines was 65% of the number of the stems. In the two-thinning regime, the first thinning was conducted at the age of 39 years when the stand basal area was 37 m2 ha–1 and the dominant height was about 15 m. After the thinning, the basal area was 27 m2 ha–1. Spruces were thinned from below, but both small and large pines were removed. The second thinning was 8 years later and much heavier: the stand basal area was decreased from 35 m2 ha–1 to 18 m2 ha–1 by removing both small and large pines and spruces. When the optimal two-thinning regime was compared to the regime presented by Forest Centre Tapio, the loss of SEV was about 30% (6070 FIM ha–1) in the case of thinnings from below, and about 20% (7250 FIM ha–1) in the case of thinnings from above.
  • Vettenranta, Kivirinnanpolku 4, FIN-40950 Muurame, Finland ORCID ID:E-mail: vettenr@cc.joensuu.fi (email)
  • Miina, Faculty of Forestry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland ORCID ID:E-mail:

Category: Review article

article id 9984, category Review article
Christoph Kogler, Peter Rauch. (2018). Discrete event simulation of multimodal and unimodal transportation in the wood supply chain: a literature review. Silva Fennica vol. 52 no. 4 article id 9984. https://doi.org/10.14214/sf.9984
Highlights: Focus on discrete event simulation, wood supply chain and multimodal transport; Analyses of 12 review articles and a core of 32 research papers, complemented by 48 related ones; Research focus from unimodal to multimodal transport to build efficient, resilient, green and socially sustainable supply chains; Development of robust risk management considering supply risks, demand risks and external risks is needed.

This review systematically analyses and classifies research and review papers focusing on discrete event simulation applied to wood transport, and therefore illustrates the development of the research area from 1997 until 2017. Discrete event simulation allows complex supply chain models to be mapped in a straightforward manner to study supply chain dynamics, test alternative strategies, communicate findings and facilitate understanding of various stakeholders. The presented analyses confirm that discrete event simulation is well-suited for analyzing interconnected wood supply chain transportation issues on an operational and tactical level. Transport is the connective link between interrelated system components of the forest products industry. Therefore, a survey on transport logistics allows to analyze the significance of entire supply chain management considerations to improve the overall performance and not only one part in isolation. Thus far, research focuses mainly on biomass, unimodal truck transport and terminal operations. Common shortcomings identified include rough explanations of simulation models and sparse details provided about the verification and validation processes. Research gaps exist concerning simulations of entire, resilient and multimodal wood supply chains as well as supply and demand risks. Further studies should expand upon the few initial attempts to combine various simulation methods with optimization.

  • Kogler, Institute of Production and Logistics, Department of Economics and Social Sciences, University of Natural Resources and Life Sciences, Vienna, Feistmantelstrasse 4, A-1180 Vienna, Austria ORCID ID: https://orcid.org/0000-0001-8811-152X E-mail: christoph.kogler@boku.ac.at (email)
  • Rauch, Institute of Production and Logistics, Department of Economics and Social Sciences, University of Natural Resources and Life Sciences, Vienna, Feistmantelstrasse 4, A-1180 Vienna, Austria ORCID ID: http://orcid.org/0000-0002-5812-4415 E-mail: peter.rauch@boku.ac.at

Category: Article

article id 5468, category Article
Seppo Kellomäki, Heikki Hänninen, Taneli Kolström, Risto Lauhanen, Ulla Mattila, Brita Pajari, Hannu Väisänen. (1992). A simulation model for the succession of the boreal forest ecosystem. Silva Fennica vol. 26 no. 1 article id 5468. https://doi.org/10.14214/sf.a15626

A model for the succession of the forest ecosystem is described. The growth and development of trees and ground cover are controlled by temperature and light conditions and the availability of nitrogen and water. In addition, the effects of the annual cycle of trees including the risk of frost damage, wild fire, and wind damages are contained in the model as factors which control the survival and productivity of trees. The model also makes it possible to evaluated the risk of insect attack assuming that this risk is inversely related to the growth efficiency of trees.

The PDF includes an abstract in Finnish.

  • Kellomäki, ORCID ID:E-mail:
  • Hänninen, ORCID ID:E-mail:
  • Kolström, ORCID ID:E-mail:
  • Lauhanen, ORCID ID:E-mail:
  • Mattila, ORCID ID:E-mail:
  • Pajari, ORCID ID:E-mail:
  • Väisänen, ORCID ID:E-mail:
article id 5449, category Article
Timo Pukkala, Taneli Kolström. (1991). Effect of spatial pattern of trees on the growth of Norway spruce stand. Silva Fennica vol. 25 no. 3 article id 5449. https://doi.org/10.14214/sf.a15603

The simulation model consists of a method to generate theoretical Norway spruce (Picea abies (L.) H. Karst.) stands, and a spatial growth model to predict the growth of these stands. The stand generation procedure first predicts the tree diameters from a few stand characteristics and from tree locations. Tree age and height are predicted using spatial models. Spatial growth models were made for both diameter growth and basal area growth. Past growth was used as a predictor in one pair of models and omitted in another pair. The stand generation method and the growth models were utilized in studying the effect of tree arrangement and thinning method on the growth of a Norway spruce stand.

The PDF includes an abstract in Finnish.

  • Pukkala, ORCID ID:E-mail:
  • Kolström, ORCID ID:E-mail:
article id 5301, category Article
Birger Solberg. (1986). Forest sector simulation models as methodological tools in forest policy analysis. Silva Fennica vol. 20 no. 4 article id 5301. https://doi.org/10.14214/sf.a27757

The usefulness of forest sector models in forest policy analysis is discussed, mainly based on experiences from Norway. Forest sector modelling is contrasted to two alternative approaches: (i) Intuitive, verbal analysis, and (ii) econometric models. It is concluded that forest sector models, properly developed in contact with the policy makers, should be of considerable value in forest policy analysis.

  • Solberg, ORCID ID:E-mail:
article id 7676, category Article
Jussi Saramäki. (1992). A growth and yield prediction model of Pinus kesiya (Royle ex Gordon) in Zambia. Acta Forestalia Fennica no. 230 article id 7676. https://doi.org/10.14214/aff.7676

The study presents a growth and yield prediction model for a Pinus kesiya (Royle ex Gordon) stand by diameter classes. The material consists of temporary sample plots taken from a plantation inventory, of permanent sample plots established in commercial compartments and of an espacement trial. The mean basal area of the stand, variance and skewness of the diameter distribution are predicted. From these variables the parameters of the Weibull function are derived. Site class is assumed to be known or is calculated from measured information. Mortality is also predicted by estimating the number and mean size of dead trees. Thinnings are defined by the number of trees removed and by their relative size. If measured tree level data at the initial situation is available it can be utilized in the predictions, however, simulations can also be performed with stand level information. The minimum information needed for the prediction is planting density, site class as well as the times and removals of thinnings.

The calculations show that by decreasing the planting density of P. Kesiya from the present 1,330 stems/ha or by conducting early precommercial thinning both the relative and absolute amount of large sawlogs in the total production increase. An increase in the present planting density only slightly increases total yield. It is obvious that the presently recommended rotation of 25 years is too short for producing large sawlogs, especially on poor sites. This rotation period is suitable for small sawlog production while for pulpwood regimes shorter rotation periods can be used. If thinnings are done before the maximum current annual growth is reached stands will react well, but later on the ability to respond to thinnings decreases rapidly. Thinnings from below accelerates the production of large sawlogs more than thinning from above or systematic thinning. If all sawlog sizes are considered no great differences between thinning type exist. The study recommends different thinning regimes according to site class. Separate programs are recommended for the production of sawlogs and pulpwood.

The used thinning reaction model needs refinement and further studies with annual measured thinning trial material.

The PDF includes a summary in Finnish.

  • Saramäki, ORCID ID:E-mail:

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